It somewhat depends on whether the slab is 2cm or 3cm thick. Some stones can be stained by some glues. In the ones I've done in my home, the fabricator said just use silicon...it cushions and hold it in place. Especially if it is a 3cm slab, gravity and the silicon will hold it in place fine. You DO need to ensure that the cabinet is shimmed so the top is level, as the stone will not like it if the surface is twisted and not level.
If it is a 2cm slab, it's not a bad idea to put some plywood inserted so you have some support. Mount it on ledger boards so it is flush with the top of the cabinet.